1. Field of the Invention
The present invention relates to wireless communication systems, and more particularly to transmission protocols used by third-generation (3G) wireless communication systems.
2. Description of the Related Art
One category of mobile telephony communication devices, or mobile phones, includes third-generation devices. Third-generation (3G) mobile phones use digital radio signals for communication with cell towers, also known as base stations. Third-generation mobile phones are able to simultaneously transfer multiple data streams, such as voice, e-mail, instant messages, and streaming audio or video. Third-generation mobile phones additionally allow for high rates of data transfers and broadband capabilities. The high rates of data transfers rely on efficient organization and transmission of data to and from the applications running on a mobile phone. The organization and transmission of data is defined by protocols and standards.
Third-generation mobile phone standards are set by the Third Generation Partnership Project (3GPP) and are based on Universal Mobile Telecommunications System (UMTS) network technology. UMTS evolved from Global System for Mobile Communication (GSM) network technology. The 3GPP comprises several Technical Specification Groups (TSGs) that are responsible for various areas of third-generation technology. One way to categorize 3G technology is by layer levels and protocols. The 3G protocol stack includes at least three layers: (i) layer 1, also known as the physical layer, (ii) layer 2, also known as the data link layer, and (iii) layer 3, also known as the network layer. The physical layer handles communication between the mobile phone and a base station, the data link layer interfaces between the physical and network layers, and the network layer handles communication with applications on a mobile phone.
Layer 1 architecture and design is specified by Working Group 1 (WG1) of the Radio Access Network (RAN) TSG. This includes the specification of the physical channel structures, the mapping of transport channels to physical channels, spreading, modulation, physical layer multiplexing, channel coding, and error detection. Among the technical specifications (TS) provided by TSG RAN WG1 is TS 25.212, which is a multiplexing and channel-coding specification. TS 25.212 is periodically updated and multiple releases are published, including in conjunction with new releases of the 3GPP standard. A list of releases of TS 25.212 is presently available on the Internet at http://www.3gpp.org/ftp/Specs/html-info/25212.htm.
Layer 2 architecture and design is regulated by Working Group 2 (WG2) of the RAN TSG, which is in charge of the radio interface architecture and protocols (Media Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP)), the specification of the Radio Resource Control (RRC) protocol, the strategies of radio resource management, and the services provided by the physical layer to the upper layers. Among the technical specifications (TS) provided by TSG RAN WG2 is TS 25.321, which is the MAC protocol specification. TS 25.321 is periodically updated and multiple releases are published, including in conjunction with new releases of the 3GPP standard. A list of releases of TS 25.321 is presently available on the Internet at http://www.3gpp.org/ftp/Specs/html-info/25321.htm. The MAC protocol specifies, among other things, (i) communication channels and (ii) protocol data units (PDUs), formats, and parameters, for communication between the physical layer and the RLC layer of a mobile phone.
Release 5 of the 3GPP standard introduced the High-Speed Downlink Packet Access (HSDPA) protocol, which allows for the high-speed download of data to a mobile telephony device, referred to as user equipment (UE), from a base station, referred to as a Node-B. A Node-B is part of the UMTS Terrestrial Radio Access Network (UTRAN). Releases 6 and 7 of the 3GPP standard also include the HSDPA protocol, and later releases are expected to include it as well.
A MAC-layer entity called MAC-hs (MAC-high speed) controls a High Speed Downlink Shared Channel (HS-DSCH) that is used by the HSDPA protocol. A MAC-hs entity in a UE performs functions related to, but different from, the functions of a MAC-hs entity in a corresponding Node-B with which the UE is communicating over an HS-DSCH. An HS-DSCH might carry data for multiple UE processes. Unless otherwise indicated, references herein to entities refer to logical entities in a UE.
The operations of functional units in 3GPP-compatible devices operating according to the 3GPP standard are not necessarily optimized. Efficiency improvements in 3GPP-compatible devices could reduce power consumption by UEs and/or per-unit manufacturing costs for UEs.